This invention relates to a pressure medium control means for hydraulic servo-steering devices provided with a pressure source and preferably a hydraulic pressure accumulator in which means there is included a control valve having a four-way control and one or preferably two control pistons for selectively connecting the working spaces of a servo motor with a pressure source or return line to a reservoir.
More particularly, the servo motor is in operative relationship with a power output member which affects the steerable wheels, with the power output member being connected with a power input member via elastic, preferably pre-stressed coupling means, and in which the control pistons are provided with reaction areas stressed by the pressures of the working spaces of the servo motor or are in operative relationship with respective reaction members and are actuable via actuating means by reason of relative movements between the power input member and the power output member.